The present invention relates generally to a vehicle occupant safety system and more particularly to a vehicle occupant active restraint system that determines contact with an out-of-position occupant during activation and consequently reduces activation force to reduce the possibility of injury to the out-of-position occupant. Generally, an occupant who is positioned relative to the active restraint in a manner such that full activation of the restraint may cause injury is considered an xe2x80x9cout-of-positionxe2x80x9d occupant.
Many known systems have been developed for determining the position of an occupant within a motor vehicle for the purpose of determining whether and with how much force to activate an active safety restraint such as an airbag. For example, some known systems determine if an occupant is sitting too close to an airbag and may consequently determine not to fire the airbag in the event of an accident or may determine to fire the airbag with less force.
U.S. Pat. No. 6,129,379, assigned to the assignee of the present invention, discloses an airbag module with a plurality of strips attached to the airbag. During the deployment of the airbag, the speed with which the strips are extended can be evaluated to determine the speed of deployment of the airbag.
The present invention provides an algorithm for evaluating information from sensors interacting with strips that are extended during activation of the airbag.
In one embodiment, each strip includes an alternating pattern that generates a frequency in a sensor through which the strip passes during deployment. The frequency generated is based upon the speed with which the strip passes by the sensor and, in turn, the speed of deployment of the airbag. A controller evaluates the frequency and the changes in frequency over time during deployment. Depending upon the specific configuration of the system and the specific vehicle, a decrease in the speed of deployment of the airbag may be indicated by a decrease in the frequency of the signal. A decrease in speed of deployment may indicate that the airbag is in contact with an occupant.